将值从一种形式的方法转换为另一种形式

我在使用另一种形式的形式方法时遇到问题

我这样编码:
(我在textbox1中输入了123)

i have problem with using a method of a form in another form

i coded like this:
(i entered 123 in textbox1)

public class Form1 : Form
    {
        private string user_code;

      public string UserCode
        {
            get { return user_code; }
        }

        public bool LoginUser()
        {
       user_code = null;
 
        
        if(textBox1.Text==123){
              user_code="usercode";
                 }
             * 
             */
        }
    }

和在form2中的用法:

and usage in form2:

Form1 form1 = new Form1();
            form1.LoginUser();

            MessageBox.Show(form1.UserName);

现在输出是一个空字符串，我用断点检查了一下，我发现当我在form2中调用loginuser时，textbox1中的值变为空，并且如果条件变为false 您如何看待问题?

TIA

now output is an empty string,i checked with breakpoint and i saw that when i call loginuser in form2 the value in textbox1 become empty and if condition become false
what do you think about problem??

TIA